It's states with strong central powers that make more trouble in history.

I call BS on this statement. The greatest, longest-lasting, and widest-spread nations in history, as well as those most responsible for the greatest leaps in art, science, and philosophy - Egypt, Rome, Dynastic China, Charlemagne's HRE, the Ottoman Empire, Imperial England, the modern US, etc. - have always been almost exclusively those with strong central powers. Consequently, there is no evidence to say that decentralized governments - say, Vikings, Crusaders, the post-Charlemagne HRE, Interregnum England, right on up to modern-day Mexico - have made any less 'trouble' throughout history.